1. The Technical Field
The present invention relates to a sewing yarn with at least two roving yarns, which are twisted together with one another to form the sewing yarn, whereby each roving yarn has the structure of a core yarn, which comprises at least one first multifilament yarn component forming a core, and a second fibre yarn component spun over the core, and a process for the manufacture of such a sewing yarn in which at least two roving yarns are initially manufactured, whereby, to produce each of the yarns, a slubbing made of fibre yarns is introduced into a spinning device together with the multifilament yarn component serving as the core, and is spun in said spinning device, and the at least two roving yarns are then twisted together with one another.
2. The Prior Art
Sewing yarns are known in a variety of different structures, whether as sewing thread, as air-intermingled yarns, or as core yarns, whereby each of the structures referred to has its individual advantages and weaknesses respectively.
Sewing yarns which are designed as core yarns comprise at least two roving yarns, whereby these roving yarns, at least two in number, designed as core yarns, are processed by twisting to make finished sewing yarn. Each of these roving yarns in this situation has the structure of a core yarn, of such a nature that each roving yarn encompasses at least one core made of a first multifilament yarn component, whereby this core is then spun with a second fibre yarn component. In other words, a roving yarn of this type has a core- enveloping fibre or sheath structure, whereby the core is formed by the interior multifilament core, designated hereinafter as the first core component, and the sheath is formed by a fibre yarn which surrounds the core and is designated hereinafter as the second yarn component or the second fibre yarn component.
Because the second fibre yarn component or the sheath component in such known core yarns is intended to cover the first multifilament yarn component, which provides a major part of the strength of the finished sewing yarn, to provide protection against undesirable damage during sewing, persons skilled in the art have hitherto considered it necessary for such thread covering with fibre yarn to be necessarily so dense that the sewing yarn created from two roving yarns must feature, viewed in the cross-section of the sewing yarn, at least about 45 individual fibres per roving yarn, but as a rule between 50 and 88 individual fibres per roving yarn. This leads to a situation, however, in which such core yarns can only be manufactured with relatively high costs expenditure, due to the relatively high usage of fibre yarn.
The object underlying the present invention is to provide a sewing yarn of the type described, which comprises the structure of a core yarn, and which can be manufactured in a more economical manner than hitherto.
This object is achieved according to the invention by a sewing yarn with at least two roving yarns, which are twisted together with one another to form the sewing yarn, whereby each roving yarn has the structure of a core yarn, which comprises at least one first multifilament yarn component forming a core, and a second fibre yarn component spun over the core, characterized in that, viewed in the cross-section of the sewing yarn, the spun fibre yarn covering of at least one roving yarn contains less than 41 individual fibres.